During the past grant cycle, working in Araihazar, Bangladesh, where there is a wide range of both[unreadable] arsenic (As) and manganese (Mn) in drinking water, we have demonstrated that both elements have adverse[unreadable] effects on child intelligence. The current proposal seeks to further test and elaborate on the hypotheses that[unreadable] exposure to As and Mn are associated with deficits in intellectual function in two distinct population samples.[unreadable] The first draws on a U.S. population, for whom we are able to apply standardized scores to estimate the[unreadable] magnitude of the association with IQ. The second draws on a Bangladesh population to examine whether or[unreadable] not the effects of As on intellectual function are reversible; it takes advantage of a Columbia Earth Institute[unreadable] initiative to provide As-free deep tube-well water to an exposed population in Araihazar, Bangladesh.[unreadable] In New Hampshire (NH), we will conduct a cross-sectional study of 500 fourth-grade children to examine[unreadable] the relations between water As, water Mn and IQ. We selected schools to yield a sample in which roughly[unreadable] 70% will consume water from wells with < 10 ug As/L, 30% from wells with >10 ug/L, based on USGS data.[unreadable] The distribution of Mn in wells is less well characterized, but limited USGS data indicates that roughly 10% of[unreadable] wells in this region will have Mn concentrations above the EPA Health Advisory Level of 300 ug/L.[unreadable] In Bangladesh, we will test the hypothesis that provision of low As/low Mn tube wells is associated with[unreadable] improved intellectual function. We propose a two-year prospective study of 300 children (baseline ages 7-9)[unreadable] in Araihazar, Bangladesh. For each of the following 4 groups, 75 children will be recruited: a) low As, low[unreadable] Mn; b) low As, high Mn; c) high As, low Mn; d) high As, high Mn. Based on EPA guidelines, the definition of[unreadable] "low As" will be < 10ug/L, and "low Mn" will be < 300 ug/L After their initial intellectual assessment, children[unreadable] with high As wells will be provided access to low As/low Mn community wells and education to promote their[unreadable] use. Children will be assessed before remediation and at 12- and 24-months post-remediation.[unreadable] Given that in the U.S., approximately 1.3 million people are exposed to > 10 ug/L As in drinking water,[unreadable] and household Mn, though less well characterized, is known to be elevated in several states (e.g. PA, NH),[unreadable] identification of adverse effects on childhood intelligence may have significant impact both on public health[unreadable] and on establishment of policies to reduce exposure.